| Abstrakt: |
This study investigates the morphology and occurrence of the potentially toxic invasive cyanobacterium recently detected in Serbia, Sphaerospermopsis aphanizomenoides(Forti) (Zapomelová et al. 2010), in correlation with several environmental parameters. The presence of this species was recorded during warm months in three of four studied sites in the Ponjavica River. It was found in a community with invasive Cylindrospermopsis raciborskii(Woloszynska) (Seenayya and Subba Raju 1972) and Raphidiopsis mediterranea(Skuja 1937) in this small, shallow, eutrophic river, with slow water flow. The peak of its abundance was observed in August 2008 (3.36 × 106cell/ml). The proliferation of this cyanobacterium was caused by very high water temperatures at the beginning of the summer, which resulted in an increase in the biomass of this species in August. The blooms of S. aphanizomenoidesoften occur under nitrogen depletion due to the formation of heterocysts, but in our study, their number was in positive correlation with the concentration of total dissolved nitrogen at the end of the study period. However, PCA analysis, which included the whole study period, indicated that there is a negative correlation between these two parameters. According to this analysis, in this locality, the factors which control the formation of the akinetes of S. aphanizomenoidesare both the concentration of phosphate in the water and temperature. The morphological characteristics (trichome length, dimensions of the vegetative cells, heterocysts and akinetes, and their position) of this species, first recorded in Serbia, were mainly in correlation with those from the Czech Republic. However, individuals of S. aphanizomenoidesfrom Serbia have shown a greater range of morphological variability than previously recorded. |
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